Toys, ornamental shapes or any other geometrical figures which remember their original shapes are the object of this patent. Some form regaining toys go back to their original shape after an external stimulus which caused their original deformation has been removed. But they do so at some fixed rate which is not controllable by a user unless he applies an extra stimulus to the toy. Some other toys change their shape only when a user applies a stimulus upon it. But they only do so while they lose their structure integrity, preventing a possibility of repeated use of the toy without extensive corrective readjustments. This patent concerns with toys which regain their prefixed original shape only when a user applies a stimulus upon it, and at the same time, without losing its structural integrity so that the toys can be used repeatedly.
There is a host of alloys, called shape memory alloys. When an alloy of this group is annealed at a very high temperature (typically 1000.degree. C. or above) in a given shape, the shape is fixed permanently unless it is annealed once again. If the alloy is cooled down below a certain temperature (typically 45.degree. C..about.80.degree. C.), called a transition temperature, it becomes quite weak mechanically and can thus be deformed relatively easily. After the deformation, if the temperature of the alloy is raised above the transition temperature, it recovers its originally fixed shape by changing phase of its crystal structure. Both the annealing temperature and the transition temperature depend on alloys.
An example of the shape memory alloy in Nitinol. This is made of nickel, titanium, a small amount of iron and a small amount of nitrogen. In metallurgical terms, this can be expressed as:
Ni-(40.about.52)Ti-(0.about.0.1)Fe-(0.about.0.1)N PA1 Cu-(13.about.16)Al-(3.about.6)Ni, PA1 Au-(4018 55)Cd, PA1 Cu-(18.about.25)Zn-(5.about.7)Al, PA1 Cu-(12.about.16)Sn
Where the numbers in parentheses indicate ranges of weight percentage of each following element. Other examples of shape memory alloys are:
and other alloys such as Ag-Cd, Ag-Zn, Cu-Al, Cu-Zn, Fe-Bn, Fe-Pt, In-Tl, Nb-Ti, Ni-Al, etc.
An object of this invention is to make toys and other objects with shape memory alloys so that they regain their prefixed shapes upon a heat supply by a user after they are deformed for any purpose.
Another object of the invention is to make the toys repeatedly usable without permanently damaging them after each use.
Another object of the invention is to cover the alloys with soft plastics to improve the appearance of the toys.
Other objects of the invention will become apparent to those skilled in the art in the light of the following description.